/*
 * Copyright (c) 2011, 2024, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package jdk.graal.compiler.graph.iterators;

import java.util.Iterator;
import java.util.NoSuchElementException;

import jdk.graal.compiler.graph.Node;

public abstract class NodeIterator<T extends Node> implements Iterator<T> {

    protected T current;

    protected abstract void forward();

    @Override
    public boolean hasNext() {
        if (current != null) {
            return true;
        }
        forward();
        return current != null;
    }

    @Override
    public T next() {
        /*
         * Normally hasNext() should call forward(). Only call it here if current is null,
         * indicating users calling next() without calling hasNext() first.
         */
        if (current == null) {
            forward();
        }
        T ret = current;
        if (current == null) {
            throw new NoSuchElementException();
        }
        current = null;
        return ret;
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException();
    }
}
